Humans occupy, use, and inhabit many different kinds of structures and spaces on the ground, above the ground, under the ground, and even underwater. These structures and spaces are frequently in constant use around the clock, and adequate lighting to support their occupation, use, and habitation by humans is necessary. Most ground level and above the ground structures and spaces can receive at least some of the illumination required from sunlight. Underground and underwater spaces and structures generally cannot receive solar illumination and must rely on artificial light to support human occupation, use, or habitation. Without adequate light, humans would not be able to work, use, or live in such structures and spaces as subways, mines, underground storage and like facilities, underwater areas in offshore drilling rigs, tunnels, factories, warehouses, hospitals, libraries, schools, theaters, apartment buildings, hotels, stores, shopping malls, office buildings, military installations, restaurants, houses, airports, bridges, roads, highways or anywhere that requires lighting beyond natural light. The range of structures and spaces used, occupied, or inhabited by humans is very extensive.
Providing adequate interior or exterior illumination for structures and spaces such as those described above can present challenges. Underground and underwater structures and spaces like mines, subway and other tunnels, and drilling rigs, for example, never receive natural light, and all illumination must be artificial. Enclosed commercial and industrial structures like factories, warehouses, hospitals, shopping malls, and airports, for example, have few or no windows to let natural light into the interior and rely virtually entirely on artificial lighting. Very few of the structures described above have windows or skylights that let in sufficient natural light to illuminate their interiors, and light must be supplied by artificial sources.
Interior lighting must often be capable of illuminating structures or spaces around the clock to accommodate their continuous use without interruption when these structures or spaces must be used or occupied 24 hours a day. Interior and exterior illumination frequently must be maintained beyond usual working hours for security reasons. Many facilities, such as retail stores, schools, and libraries, for example, are lighted during the day as well as beyond business hours. In addition, the intensity of the artificial light supplied must be sufficient to enable those working in an interior space to perform their jobs.
In some exterior spaces, such as, for example, along airport runways, at street intersections, along subway and railroad tracks, and at railroad crossings, specific lighting is required to be on continuously at all times without interruption for safety reasons. In other above ground exterior spaces, such as adjacent to the exteriors of buildings, lighting is required only at night. The intensity of exterior lighting, whether it is required during the day, at night, or around the clock, must be sufficient to achieve its purpose. For example, the lighting provided along an airport runway, taxiway, or other ground area must clearly highlight the boundaries of these areas at all times to enable the aircraft to locate them accurately during landing, take off, and taxi.
The cost of the electric power required to power interior and/or exterior illumination, particularly for large structures and spaces, depends on current energy costs and can be a sizeable part of a business or municipality's operating budget. The use of compact fluorescent and standard fluorescent light sources may reduce costs, but a significant amount of heat can be generated by these and other interior lighting sources, which leads to increased costs for cooling the interior of a facility during hot weather. Sodium vapor lighting used for exterior lighting, such as street and highway lighting, presents similar challenges.
Skylights have been installed in many enclosed structures to let natural light info the interiors. While skylights may effectively increase the amount of natural light that enters a building, they can act as undesirable heat sinks, are costly to install and can present continuing maintenance problems. The installation of a skylight requires an opening to be cut in a building roof. The joint between the skylight and the roof is susceptible to leaking, and must be carefully sealed upon installation and maintained to insure that it is water-tight to avoid water damage inside the building. If the joint is not properly sealed, exterior air may also flow into the building, creating drafts and interfering with heating and cooling. The cost of repairs to skylights can exceed the costs of roof repairs. Additionally, skylights must be washed on a regular basis to maximize their effectiveness in admitting natural light into a building.
To reduce power costs, solar cells have been adapted to provide power for interior lighting in built structures and in underground spaces, such as mines, for example. Solar cells have also been used to provide power for exterior lighting in many structures and spaces. Street lights and outdoor security lighting, for example, are available with solar cells. If the foregoing examples employ currently available solar cells, complex circuitry and controllers are required, and the cost of the electronics can significantly exceed the cost of the solar cell. As a result, the desired cost savings for these types of solar cells have not been achieved.
The use of solar cells to power light sources of different types is known in the art. U.S. Pat. No. 7,766,504 to Holin, U.S. Patent Application Publication 2010/0126549 to Ryu, U.S. Patent Application Publication 2008/0123328 to Lai et al, and U.S. Patent Application Publication 2006/0220895 to Arcaria et al, for example, ail describe solar-powered illumination devices including a solar cell that is exposed to sunlight, a battery or like structure that stores the power produced, and an LED light source that emits light when sunlight is not available. The devices described in this patent and these publications include complex electronics. They are intended to be used only as outdoor illuminating devices. It is nowhere suggested that these solar-powered structures could be modified to provide a primary source of artificial interior illumination for the interior of an enclosed structure or that they could provide a reliable source of inexpensive illumination for exterior or underground uses.
The use of solar cells and light-emitting diode (LED) lighting sources to illuminate interior areas has been described in the art. In U.S. Pat. No. 7,057,821, for example, Zincone discloses an integrated natural and artificial lighting system to provide light to the interior of a building. In this system, natural light is converted to electricity by a photovoltaic (PV) cell and stored in a battery until it is used to power LED or fluorescent lights, which provide artificial light when natural light is not available. A connection to an external power source is available for backup when needed. The system described by Zincone is specifically adapted to be placed within a light shaft or skylight in the roof of a building, and there is no suggestion whether this system would be functional other than as part of the light shaft or skylight assembly disclosed to be integral components of the system. Consequently, all of the challenges associated with skylights accompany the Zincone lighting system. The Zincone system, moreover, includes complex circuitry and a heat exchanger to deal with the heat generated in the skylight. The use of this system to provide exterior illumination is not suggested.
The provision of solar lighting to enclosed quarters, such as tunnels, mines, factories, theaters, stores, restaurants, office, and homes, where a substantial amount of electrical energy is used during daylight hours to maintain lighted interiors is disclosed in U.S. Pat. No. 4,279,000 to Fries and suggests augmenting the system described with regular lighting. However, the Fries system employs a rather complex arrangement of a solar collector and fiber optic cables to collect and transmit solar light to light distribution devices. Latter, in U.S. Pat. No. 4,246,477, describes an artificial and solar lighting system for a building that directs a solar beam through a light transmission channel to a location within the building where light is distributed to light fixtures. The light fixtures also have fluorescent tubes that automatically generate backup artificial light. The light distribution channel described by Latter requires an opening to be cut in the building roof so that this system, has all of the disadvantages associated with providing natural light through a skylight. Neither of the foregoing systems provides an illuminator useful for exterior lighting.
Other lighting systems have been disclosed that employ a combination of solar cells and LED lighting to illuminate building interiors. U.S. Patent Application Publications 2011/0107689 to Holguin et al and 2009/0085497 to Osborn describe such interior lighting systems. The systems described in both of these publications, however, also are specifically adapted for use in skylights or light tubes installed in a building roof. Additionally, both systems have control systems of the type that are relatively complex and potentially costly. Holguin et al does suggest that a standard voltage supplemental lighting system powered by on-grid power could be included in the control system. Neither Holguin et al nor Osborn, however, even remotely suggests that their systems could be adapted for installation or use other than with a skylight or light tube or that their use to illuminate exterior structures or spaces is possible.
The prior art, therefore, fails to suggest a system or method for generating artificial light to illuminate interior and exterior structures and spaces without using skylights or similar light-directing structures that employs various combinations of solar photovoltaic-generated power and conventional power without complex circuitry to directly power LED or other light sources to provide required interior or exterior illumination.